The present invention relates to load bearing fabric, and more particularly to attachment components and methods for securing load bearing fabric to a support structure.
The term xe2x80x9cload bearing fabricxe2x80x9d is commonly used to refer to a class of high strength, highly durable textiles that are typically woven from elastomeric monofilaments and conventional yarns. Some of today""s conventional load bearing fabrics have greater strength and durability characteristics than spring steel and other conventional load bearing materials. In addition to their strength and durability characteristics, load bearing fabrics are lightweight and typically have a high modulus of elasticity. Because of the inherent elasticity, load bearing fabrics do not require cushioning like conventional rigid load bearing structures. Therefore, load bearing fabrics are well-suited for use in a variety of applications where a strong and durable yet lightweight or elastic load bearing surface is desired, for example, in seating, cots and wheelchair applications. Further, load bearing fabrics are aesthetically pleasing and can be exposed during use, for example, as the seat or back of an office chair. The use of load bearing fabrics continues to increase dramatically with the continued development of stronger, more durable and aesthetically pleasing fabrics.
One particularly important challenge related to the use of load bearing fabric is the attachment of the fabric to the support structure. Although load bearing fabrics have high strength and durability characteristics, they must be properly attached to the support structure to provide an end product with the desired strength and durability. Conventional attachment methods often fail to provide the necessary strength and durability to withstand the forces applied to the fabric. As a result, the fabric separates from the support structure under conditions that the fabric is otherwise well-suited to survive. In some applications, the bond itself may fail and in other applications, the method of attachment may cause the textile to unravel or separate along the periphery of the fabric. Accordingly, there is an ongoing effort to develop new and improved methods and components for securing the load bearing fabric to the support structure.
Typically, load bearing fabrics are secured to a support structure by a carrier, often in the form of a peripheral frame. The fabric is first attached to the carrier and then the carrier is attached to the support structure using fasteners or other conventional techniques and apparatus. In such applications, the challenge is to intersecure the fabric and carrier in a way that provides a strong and durable bond without damaging or promoting unraveling of the fabric. One conventional method for securing load bearing fabric to a carrier includes the use of encapsulation. In general, encapsulation involves the molding of a carrier about the peripheral edge of the fabric in an in-molding process. During the molding process, the material of the carrier flows through (e.g. through the spaces between the warps and wefts of the fabric) and becomes intimately intersecured with the fabric. Although encapsulation typically provides a strong, durable bond between the fabric and the carrier, it requires expensive molding machinery.
The fabric can also be attached to the carrier or directly to the support structure by heat fusion. An example of this process is described in U.S. Pat. No. 4,928,334 to Kita entitled Joint Structure For Fabric Web Having High Modulus Of Elasticity. In this process, the fabric is looped around a rod and is folded back onto itself. A heat-fusible resin film is disposed between the folded and unfolded layers, and the two layers are fused together using high-frequency welding. The resulting bond is relatively strong and is not prone to unraveling; however, it is relatively complex in that it requires the use of high-frequency welding apparatus. This process is also limited for use with applications where the fabric can be folded back onto itself, thereby limiting the construction and configuration of the frame as well as the shape and design of the fabric.
Another method for securing the fabric to the support structure is to sew the fabric to the carrier or to the support structure. Sewing can also be used in applications where the fabric is looped or wrapped around a carrier or a support structure and then sewn back onto itself. Although relatively inexpensive, these sewing methods suffer in that sewing randomly damages the structural threads of the fabric, and consequently weakens the fabric and the attachment.
Another conventional attachment method is to adhesively secure the fabric to the carrier or directly to the structural support. For an adhesive bond to provide sufficient strength and durability for conventional applications, the fabric must be wrapped around the carrier or the support structure and then adhesively secured back onto itself, much like the fused construction described above. Primarily as a result of the friction between the fabric and the carrier, this xe2x80x9cwrappedxe2x80x9d construction dramatically reduces the amount of forces that must be borne by the adhesive bond. Although adhesive is relatively inexpensive, this method requires substantial labor and provides an aesthetically undesirable part, suitable only as a class xe2x80x9cBxe2x80x9d surface (i.e. a surface that must be covered).
The aforementioned problems are overcome by the present invention wherein a bonding strip is provided with bonding grooves that receive an adhesive to create mechanical and adhesive connections between the bonding strip and the fabric. The bonding strip includes a pair of bonding strip halves that are sandwiched about the fabric and are intersecured by an adhesive. The inner surfaces of the bonding strip halves are shaped to define bonding grooves that are filled with adhesive as the bonding strip halves are secured to the fabric. The adhesive cures within the bonding grooves and the spaces within the fabric to provide a strong, mechanical bond between the fabric, the adhesive and the bonding strip halves.
In a preferred embodiment, the bonding grooves are dovetailed or otherwise undercut in cross-sectional shape to provide enhanced mechanical resistance to separation of the adhesive from the bonding strip halves. The undercut cross-sectional shape is particularly helpful in resisting the component of separation forces that extend perpendicular to the plane of the fabric.
The present invention also discloses a method for attaching a load bearing fabric to a support structure. The method generally includes the steps of (a) providing a pair of bonding strip halves, each half defining bonding grooves adapted to receive adhesive, (b) applying an adhesive to one or more of the bonding strip halves, (c) closing the bonding strip halves about the fabric, whereby the adhesive flows through the fabric and into the bonding grooves in both bonding strip halves, (d) permitting the adhesive to cure to create adhesive and mechanical bonds between the fabric and the bonding strip halves and (e) securing the bonding strip to the support structure.
The present invention provides a simple and effective method for attaching a bonding strip to a load bearing fabric. The combination of mechanical and adhesive bonds between the bonding strip, adhesive and fabric provides a strong and durable interconnection. Also, the bonding grooves increase the surface area of the bonding strip that is in contact with the adhesive, thereby increasing the strength of the adhesive bond between the adhesive and the bonding strips halves. The bonding strip halves can be inexpensively manufactured using conventional extrusion or molding equipment. Further, the bonding strip halves can be easily secured to the fabric with adhesive using conventional jigs and fixtures. An additional benefit of the present invention is that it provides a class xe2x80x9cAxe2x80x9d surface (i.e. one that does not require covering) because the adhesive is sandwiched between the bonding strip halves. Accordingly, the present invention provides for an attractive and inexpensive yet strong and highly durable attachment.
These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.